Electric power system



ELECTRIC POWER SYSTEM Filed Sept. 20 1944 AMPERE BATTE Y .JEc TION No.1

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His Attorney.

Patented Feb. 25, 1947 2,416,601

UNITED STATES PATENT OFFICE ELECTRIC POWER SYSTEM John R. Williams,Schenectady, N. Y., assignor to General Electric Company, a corporationof New York Application September 20, 1944, Serial No. 554,944

10 Claims. (Cl. 171118) This invention relates to electric power systemsand more particularly to improvements in automatically controlledmultiple-unit electric power pply systems.

When power is to be supplied to a load which Referring now to the singlefigure of the accompanying drawing, which illustrates diagrammaticallyan embodiment of the invention, two power supply units are shown, by wayof example, as comprising direct-current generators I and v2 which maybe driven by any suitable means, such,

for example, as by motors (not shown). These generators have theirnegative terminals connected directly to the negative side or conductor3 of a load bus and have their positive terminals connected to thepositive side or conductor 4 of a load bus through the contacts ofrespective line cont-actors 5 and 6.

The load which is connected between the conductors of the load buscomprises, by way of example, a plurality of similar battery sections.Battery section No. 1 consists of a plug and socket type connector 1into which the connections from a battery to be charged, such, forexample, as a 5 battery 8, may be plugged. In series with this is widelyvariable it is often more economical to receptacle is a resistor 9 forcontrolling the charguse a number of relatively small power sources ingcurrent, an ampere-hour meter I 0 and the than one large source becausethe number of contacts of a battery contactor H. The amperesmall unitsin service at any one time can be hour meter has apair of normallyclosed contacts varied with variations in load so as to keep each 10connected in series with the operating coil of a unit in operation atapproximately full load and battery relay l2 whose terminals areconnected maximum efliciency, whereas a single unit large across thecontacts of the battery receptacle so enough to carry the maximum loadwill operate that when a battery is plugged in the voltage of aconsiderable length of the time at part load and the battery Will n i tbattery relay D hence at relatively low efficiency. vided theampere-hour meter contacts are closed.

In accordance with this invention there is pro- I'he battery relay l2has a Set f no m l y Open vided a novel control system for automaticallycontacts which control the connections of the varying the number ofpower sources which are operating coil of the battery contactor llbetween in operation in proportion to the total load. and the main loadbus conductors 3 and 4. The for preventing the overloading of any of theunit battery relay I2 also has tWo additional sets of power sources. Theinvention is particularly normally open contacts which are connectedadapted to the control of motor generator sets across control circuitsl3 and M respectively. which are used for charging storage batteriesThese latter circuits control the starting and and the invention ischaracterized by automatic stopping of the generators I and 2respectively,

' means for dropping part of the load temporarily, as will be describedmore fully below.

in case n overload f one u i t n Additional duplicate battery sections,such as until such time as another power unit is availsections 2. i smay l b connected able for Sharing the loadbetween the main loadconductors 3 and 4 but An object of the invention is to provide a new inorder t simplify t drawing only t a improved electric D Systemnectionsleading from the control circuits l3 and Another object of the inventionis to provide a H to the normally open contacts of the battery new andimproved automatic battery charging relays of these sections are shown,ystem. In order to prevent overloading of one of the A further object ofthe invention is to provide generators an isolating contactor l5 has twosets a ne a d mpro e l a Control System for of normally open contactswhich are connected ni p p t Electric power pp y y e serially in theconductors 3 and 4 respectively. The invention Will be better understoodfrom Additional battery sections are connected between the followingdescription taken in connection t conductors 3 d 4 beyond th t t of Withthe accompanying drawing and its Scope the isolating contactor, theseadditional sections Will be pointed Out in e pp Claims. being indicatedas sections No. 7 to No. 10 inclusive. These sections may be duplicatesof section No. 1 and, as shown, section No. 7 comprises elementscorresponding to those of section No. 1. Sections Nos. 8-10 inclusivecorrespond with the other battery sections and, as in the case ofsections Nos. 2-6 inclusive, only the conductors leading from thecontrol circuits l 3 and I 4 toward the normally open contacts of thebattery relays of these sections have been shown.

The operation of the isolating contactor I5 is controlled by a loadcurrent relay l6 whose operating coil is connected serially in thepositive load bus 4 and which has a set of normally closed contacts llwhich control the connections of the operating coil of the isolatingcontactor contacts of the isolating contactor, that is to say,

if the battery sections Nos. 7-10 inclusive are in operation and onlyone or two of sections Nos. 1-6 inclusive are in operation, then thepicking up of the load current relay I6 and thesubsequent dropping outof the isolating contactor I5 will result in a pumping action becausethe dropping of most of the load will cause the load current relay IE todrop out again, thus causing the isolating contactor. I5 to pick upagain and .reconnect the major part of the load to the system. In orderto prevent this a timer 2D is provided.

The starting of the generator I may be conitrolled manually by closing aswitch 2i or may be controlled automatically by closing a switch 22 and,likewise, the starting of the generator 2 23 and may be controlledautomatically by closing a switch 2 3. Under automatic operation the onedirection for, say, six months and then moved I to its other positionfor thenext six months.

The generators I and 2 may be started and driven by any suitable meansand, as shown by 'Iway of example, a motor starter ifor controlling thestarting of the motor 25 is provided I a which drives generator I and amotor starter 26 is provided for, controlling the starting of themotor2a which drives generator 2. As shown, the

starting contactors. 25 and 26 are respectively provided withcontacts25a and 26a which direct- I' y. Control e tarting of the motors Ia and2a.

3 As'it is important in a battery charging sys- -;of the invention is asfollows:

term to prevent reversed current, the operation j. of the line contactor5 for generator I is con-. trolled by avoltagerelay 21 and by thestarter 25 and the operation of line contactor 6 for generator 2 iscontrolled by a voltage relay 28 and 4 by the starter 26.

g I Inorder to insure proper charging, the generat or I is provided withan automatic voltage regulator of any suitable type shown schematicallyat 29 and, similarly, the generator 2 is provided with an automaticvoltage regulator shown schematically suredivision of load when bothgenerators are operating in parallel an equalizer connection be- ;tween,the two regulators is provided by a conat 30, and in order, further, toin ductor 3 I, the connections of which are controlled by the voltagerelays 27 and 28. The con-.-

. 1 trolcircuits areenergized by any suitable source of current supply,such as by an auxiliary sup- 1 ,plycircuit .32.

The operation of the illustrated embodiment Assume that it is desired tohave the system operate automatically in such a manner that generator Isupplies all of the initial loads connected to the system. To do, thisswitches 22 and 24 are closed and swit t m ved to th e t i ne b tt 3.

may b controlled manually by closing a switch is plugged into receptacle1 of battery section No. 1 and the ampere-hour meter ID has been set toprovide the battery with the correct amount of charge the battery relayI2 will pick I up, thus connecting the battery contactor II across themain load circuit. At the same time the two lowermost sets of normallyopen contacts on the battery relay close. The set of these contactswhich is connected across control circuit It will then connect thewinding 25 of the mo- Qtor starter for generator i across the controlsupply circuit 32 through the closed contacts of the switches I9 and 22in series. The motor starter 26 will not be energized by the closure ofthe set of normally open contacts on the battery relay I2 which areconnected across the control circuit I4 because with the selector switchI9 moved to the left its contacts which are in series with the switch 22will be open. Thus, if switch I9 had been moved to the right instead ofto the left, then motor starter 26 would pick up rather .than motorstarter 25.

The picking up of the motor starter 25 will cause the driving means ormotor (not shown) for generator I to start and come up to speed in anyconventional manner. When the voltage of generator I reaches the propervalue the voltage relay 2I will pick up and thus will connect the linecontactor 5 across the generator I through a set of normally openinterlock contacts 33 on the motor starter 25. The purpose of theseinterlock contacts is-to insure that the line contactor 5 will drop outimmediately when the motor starter 25 isdeenergized so as to prevent thebatteries from feeding reversed current to the generator I as it slowsdown due to the deenergization of its motor starter. The picking up ofthe line contactor 5 completes the connection of the generator I acrossthe load circuit or, more specifically, in the diagram it connects thepositive terminal of the generator to the positive load bus 4, thenegative terminal of the generator being permanently connected to thenegative load bus 3. Battery contactor II now picks up and battery 8then'receives charging current at the proper voltage.

The application of voltage between the main load conductors 3 and 4 alsocauses the isolating contactor I5 to pick up as this contactor isconnected between these conductors through a set i of normally closedcontacts I I and through a set of normally closed contacts to bedescribed later of the generators I and 2, depending upon the positionof the switch IE), will be automatically started and brought up to speedand connected across the line so as to charge the battery at the properrate. The subsequent plugging of batteries into the receptacles of othersections will then merely increase the load on the generator which is inoperation, namely, generator I under the assumed conditions. When theload reaches the maximum value which is permissible for generator I tocarry, then the load current relay It will pick up, thus opening itscontacts H which causes the isolating contactor I5 to drop out andclosin the contacts I8 of the load current relay it which connect themotor starter 25 across the :7 control supply circuit 32 through thecontacts of switch I9, through switch 24 and through the control circuitI 4 which is closed by the contacts of a -e s t e' b t r r a The nrreestablish said connections at the expiration of a predeterminedinterval of time.

4. In combination, a pair of motor-generator sets, a load circuit, meansresponsive to the connection of a load across said load circuit forstarting one of said motor-generator sets-and connecting its generatoracross said load circuit upon its voltage reaching a predeterminedvalue, means responsive to a predetermined load on said onemotor-generator set for starting the other motor-generator set andconnecting its generator across said load circuit upon its voltagereaching a predetermined value, and means for preventing an overload onsaid one motor-generator set during the time that the othermotorgenerator set is starting and its generator voltage is coming up tothe rated circuit voltage, said last-mentioned means including loadresponsive switching means for disconnecting the generator of said onemotor-generator set from at least as much of the load on said circuit ascan overload said one motor-generator set and a time delay device set inoperation in response to operation of said switching means forcontrolling said switching means to reconnect said disconnected portionof said load to said generators.

5. In combination, a pair of generators, a load circuit, one of saidgenerators being connected to supply current up to a predetermined loadvalue to said load circuit, means responsive to a load in excess of saidpredetermined load on said load circuit for starting the other generatorand connecting it across said load circuit upon its voltage reaching apredetermined value, means for preventing an overload on said onegenerator during the time that the other generator is starting and itsvoltage is coming up to the rated circuit voltage, said last-mentionedmeans including load responsive electromagnetic switching means fordisconnecting said one generator from at least as much of the load onsaid load circuit as substantially overloads said one generator, and atime element device for insuring that the other generator once startedis brought up to speed and connected across said load ciruit regardlessof the operation of said disconnecting means.

6. In combination, a pair of motor-generator sets, a load circuit, meansresponsive to the connection of a load across said load circuit forstarting one of said motor-generator sets and connecting its generatoracross said load circuit upon its voltage reading a predetermined value,means responsive to a predetermined load on said one motor-generator setfor starting the other motor-generator set and connecting its generatoracross said load circuit upon its voltage reaching a predeterminedvalue, means for preventing an overload on said one motor-generator setduring the time that the other motor-generator set is starting and itsgenerator voltage is coming up to the rated circuit voltage,- saidlast-mentioned means including load responsive electromagnetic switchingmeans for disconnecting the generator of said one motor-generator etfrom at least such portion of the load on said circuit as cansubstantially overload said one motor-generator set, and timing meansfor insuring that the other motor-generator set once started is broughtup to speed and connected across said load circuit regardless of theoperation of said disconnecting means andfor reconnecting the generatorof said one motor-generator set to said portion of the load apredetermined interval of time after said disconnecting operation.

"I. In combination, a pair of generators, a load circuit, one of saidgenerators being normally connected to supply current up to apredetermined load value to said load circuit, means re- .sponsive to aload in excess of said predetermined load on said one generator forstarting the other generator and connecting it across said load circuitupon its voltage reaching a predetermined value, means for preventing anoverload on said one generator during the time that the. other generatoris starting and its voltage is coming up to the rated voltage of theload circuit, said last-mentioned means including load responsiveswitching means for disconnecting said one generator from at least suchportion of the load on said load circuit as can substantially overloadsaid one generator, and time element means for preventing said switchingmeans from reconnecting said one generator to said portion of the loadfor a predetermined interval of time after said disconnecting operationthereby to prevent pumping of said disconnecting means.

8. In combination, a pair of motor-generator sets, a load circuit, meansresponsive to the connection of a load across said load circuit forstarting one of said motor-generator sets and connecting its generatoracross said load circuit upon its voltage reading a predetermined value,means responsive to a predetermined load on said one motor-generator setfor starting the other motor-generator set and connecting its generatoracross said load circuit upon its voltage reaching a predeterminedvalue, means for preventin an overload on said one motor-generator setduring the time that the other motor-generator set is starting and itsgenerator voltage is coming up to the rated load circuit voltage, saidlastmentione'd means including load responsive switching means fordisconnecting the generator of said one motor-generator set from aportion of the load on said circuit, and timing means for preventingsaid switching means from reconnecting said one generator to saidportion of the load for a predetermined interval of time after saiddisconnecting operation thereby to prevent pumping of said overloadpreventing disconnecting means.

9. In combination, a pair of generators, a load circuit, one of saidgenerators being normally connected to supply current up to apredetermined load value to said load circuit, means responsive to aload in excess of said predetermined load on said one generator forstarting the other generator and connecting it across said load circuitupon its voltage reaching a predetermined value, means for preventing anoverload on said one generator durin the time that the other generatoris starting and its voltage is coming up to the rated load circuitvoltage, said last-mentioned means including load responsive switchingmeans for disconnecting said one generator from a portion of the load onsaid circuit, means for insuring that the other generator once startedis brought up to speed and connected across said load circuit regardlessof the operation of said disconnectingmeans, and time element means forpreventing said switching means from reconnecting said one generator tosaid portion of the load for a predetermined interval of time after saiddisconnecting operation thereby to prevent pumping of said disconnectingmeans.

10. In combination, a pair of motor-generator sets, a load circuit,means responsive to the connection of a load across said load circuitfor startator 2 will therefore be started and will come up to speed andwhen its voltage is of the proper value the voltage relay 28 will close,thus connecting line contactor 5 across the generator 2 through a set ofinterlock contacts 34 which cor- The picking up of line in paralleltactor when the load current relay i6 is picked up is effected byauxiliary normally open contacts 35 and 36 on voltage relays 27 and 28respectively. These contacts are connected in series and they serve toconnect the upper terminal of the operating coil of the isolatingcontactor [5 to the negative side 3 of the main circuit, the other sideof this contactor being permanently connected to the positive side i ofthe main circuit.

Under certain operating conditions the operatlon of the isolatingcontactor l5 in response to the picking up of the load current relay iswill cause the dropping of sufiicient load to result in the dropping outof the load current relay H5 so that a pumping action will occur and thegenerator 2 will never be brought up to speed. In order to prevent suchfailure a set of normally open contacts 3? on the load current relayclose as ,soon as the relay it picks up and complete an energizincircuit for the timer This timer has a set of instantaneously closingseal-in contacts 38 connected in parallel with the contacts 31 so thatthe timer immediately picks and seals in. The timer also has a set ofnormally open instantaneously closing contacts 3% which are connected inparallel with the contacts iii of the load current relay V5 so that amomentary closing of the contacts it which accompany a momentary pick-upand drop-out of the load current relay it will cause the timer to pickup and maintain the energization of the starting circuit for the secondgenerator through the contacts 39. After a predetermined time, whichcorresponds to the time required to bring the second generator on theline, a set of normally closed time delay opening contacts ill on thetimer open and deenergize the timer. However, by thistime the secondgenerator is on the line, the isolating contactor i5 is closed throughthe contacts 35 and 36 on the voltage relays for the generators; and theload current relay it is picked up so that its contacts it are closedand the running circuit of the second generatoris maintained closed.

In order to prevent the jarring action and the surges of load currentwhich would accompany a pumping action of the iso ating contactor l5 andthe load current relay it a set of normally closed contacts at on thetimer are connected in series with the contacts ll of the load currentrelay. Therefore, as soon as the timer picks up and seals in, thecircuit of the isolating contactor I5 is definitely opened and ismaintained open until the second generator comes on the line and theseries connection is completed through the contacts 35 and 36.

The load current relay Hi can be any device which will pick up at apredetermined current but it can also be a reversed current protectivedevice which will drop out the generator contactors in case the motorstarters do not have interlocks.

In case both generators are operating and the main power supply fortheir driving motors fails and service is then restored it will be notedthat my control system provides automatic protection in that as soon asthe first generator comes back on the line the line current relay itwill pick up and thus will start the second generator and bring it onthe line and during this time the isolating 'contactor will drop some ofthe load so as to pre 'vent overloadin of the first generator while thesecond one is being brought up to speed.

This arrangement of dropping load until the second generator comes onthe line can be applied to any distribution system, alternating currentor direct current, where more than one source of power is available. Iteliminates-the overloads and especially the heavy peaks of load imposedwhen the main source of supply fails and 'comes back on, thus startingthe first generator and placing very large loads on it until the secendcan be brought on theline.

While there has been shown and described a particular embodiment of thisinvention, it will be obvious to those skilled in the art that variouschanges and modifications can be made therein without departing from theinvention and, therefore, it is aimed in the appended claims to coverall such changes and modificationsas fall within the true spirit andscope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a pair of generators, a load circuit, one of saidgenerators being connected to supply current up to a predetermined loadvalue to said load circuit, means responsive to a load in excess of saidpredetermined load on said load circuit for starting the other generatorand connecting it across said load circuit upon its voltage reaching apredetermined value, and

' means for preventing an'overload on said one to said load circuit,means responsive to a load in excess of said predetermined load on saidload circuit for starting the other generator and connecting it acrosssaid load circuit upon its voltage reaching a predetermined value, andmeans for preventing an overload on said one generator during the timethat the other generator is starting and its generator voltage is comingup to the rated circuit voltage comprising automatically operatedswitching means for dropping some of the load duringsaid time andsubsequently restoring it.

3. In combination, a pair of motor-generator sets, a load circuit, meansresponsive to the connection of a load across said load circuit forstarting one of said motor-generator sets and connecting its generatoracross said load circuit upon its voltage reaching a predeterminedvalue, means responsive to a predetermined load on said onemotor-generator set for starting the other motor-generator set andconnecting its generator across said load circuit upon its voltagereaching a predetermined value, and means for tor'to a portion of saidload and a time delay device cooperating with said switching means to 9ing one of said motor-generator sets and conmeeting its generator acrosssaid load circuit upon its voltage reaching a predetermined value, meansresponsive to predetermined load on said one motor-generator set forstarting the other motor-generator set and connecting its generatoracross said load circuit upon its voltage reaching a predeterminedvalue, means for preventing an overload on said one motor-generator setduring the time that the other motor-generator set is starting and itsgenerator voltage is coming up to the rated circuit voltage, saidlast-mentioned means including load responsive switching means fordisconnecting the generator of said one motor-generator set from aportion of the load on said circuit, timing means for insuring that theother motor-generator set once started is brought up to speed andconnected across said load circuit regardless of the 10 operation ofsaid overload preventing disconnecting means, and means controlled bysaid timing means for preventing said switching means from reconnectingsaid one generator to said portion of the load for a predeterminedinterval of time after said disconnecting operation thereby to preventpumping of said overload preventing disconnecting means.

JOHN R. WILLIAMS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,626,688 Newmeyer May 3, 19271,677,715 Gittings Jul 17, 1928 2,082,110 Langabeer June 1, 1937

